Hi team
My customer is encountering an issue that they use our DRV8718Q1 but when they power up with 12V and 5V, there is an EMC issue exceeding the requirement like below:
You could see the yellow line number "1" and green line number "2", the yellow line is with the DRV8718Q1, the green line is without the DRV8718Q1. We did some tests:
(1) Software shields SPI, PWM;
(2) The hardware disconnects the SPI and the connection between the PWM and the MCU;
(3) Increase the pre-drive 5V filter capacitor;
(4) Disconnect the motor current sampling;
But none of them could improve the EMC performance, now the result is exceeding about dozen dB so need your help and suggestions to improve it.
Here is the customer schematic, due to the document sensitivity, the layout is currently inconvenient to send.
(At DRAIN/GHx/GLx/SO1/SO2 pins there are no resistors, just use wires and also without 0hom resistor)
We found that, if we do not provide the 12V and only provide the VCC=5V coming from an LDO to DRV8718Q1, the EMC result will exceed the standard and be the same like we providing both 12V and 5V to the DRV8718Q1, so we suspect when we give the 5V to DRV8718Q1, there are some blocks working internally in DRV8718Q1 which cause the EMC issue, could you please help to analyze it and offer us some debug suggestions for this EMC issue or how to improve it? Any ideas of this will be appreciated since we are running out of idea why we give the 5V the EMC has already exceeded the standard, thank you.
